Open hearth furnace and the like



8, 1936. M ROSSMAN 2,063,402

OPEN HEARTH FURNACE AND THE LIKE Filed July 17, 1953 4 Sheets-Shet 1 Dec. 8, 1936. A M ROSSMAN 2,063,402

OPEN HEARTH FURNACE AND THE LIKE Filed July 17, 1933 4 Sheets-Sheet 2 Dec. 8, 1936. A. M. ROSSMAN 2,063,402

OPEN HEARTH FURNACE AND THE LIKE Filed July 17, 1953 4 Sheets-Sheet s M MS M vi W/T/VESS:

Dec. 8, 1936.

A. M. ROSSMAN 2,063,402

OPEN HEARTH FURNACE AND THE LIKE Filed July 17, 193:5 4 Sheets-Sheet 4 U 1 I Q l;lIHHHIHIIIIHIIHHIHHIT /7 e {MT/V555: I N m/ mv me- C w m/"(g Patented Dec. 8, 1936 UNITED STATES OPEN naar t'rn FURNACE AND THE LIKE ,Auii M. Ross man, Wilmette, m, assignor to Rossman Engineering Company, Chicago, 111., a corporation of Illinois Application July 1'7, 1933, Serial No. 680,811

21 Claims.

The present invention relates generally to open hearth furnaces and the like and more particularly to methods of charging a furnace and of directing the flames in the furnace to 5 obtain greatest efiiciency ,of operation.

Heretofore, melting furnaces of the hearth type have been charged with solid materials in many small unit quantities, requiring a large number of comparatively small boxes which are filled with the solid materials to be treated in the furnace. These boxes are inserted, one. at a time into the furnace by a charging machine, where they are dumped and then withdrawn. This operation generally requires more than an hour to place a charge on the furnace hearth.

An object of this invention is to provide means for placing the entire charge of solid material. on the hearth in one operation.

Another object relates to the deposition of the material in such a manner as to obtain maximum efficiency in melting down the charge and to avoid deflecting the flames up into the roof refractories.

Other objects will be apparent from the disclosure. V

In my copending application, Serial No. 672,- 545, filed May 24, 1933, I have'disclosed a novel melting furnace having a row of burners along the front of the furnace and another row of burners along the back of the furnace. The burners are inclined downward at an angle in the order of about '30 degrees from the horizontal, firing toward the center of the furnace and downward into the base of the charge of solid material. By this method of firing the material melts from beneath and combustion occurs in contact with a large surface of charged material, the flames rising through the charge. As the lower portion melts, the molten particles drop directly into the bath without coming in contact with any colder material, the charge thereby gradually sinking into the bath. In present methods of firing, where the flames are directed at the top of the charge, the molten 45 particles run into the pile of the material and again solidify when they come in contact with the colder portion at the bottom of the pile. Thistends to seal up the openings in the pile until it approaches the form of one large lump which discourages flame penetration.

By locating the burners in two rows, firing toward each other, either in opposition or staggered, the hottest zone is down the center of the furnace where the streams of flames and hot gases meet and is, therefore, at a maximum distance from the refractories, tending toward a comparatively long life of the furnace.

Operation with the burners staggered has the advantage that during the refining period the impact of the gases of combustion against the surface of the bath will set up currents or movements in the surface of the bath. This circulation provides a stirring action which tends to accelerate the contacting action of the various ingredients of the bath and thereby to accelerate the chemical reaction between them and so to hasten the refining process, as is known to those skilled in the art.

Operation with staggered burners can obviously be obtained by the furnace arrangement of Figure 2 by shutting off alternate burners during the refining operation.

As the roof is no longer needed to direct the flames, as in the case of the conventional open hearth furnace, in my above-mentioned application the roof is built at a greater height above the hearth, which provides more space for the pas ge of the burned gases and also contributes to the lengthening of the life of the refractories by the further removal from the zone of maximum temperature.

In the present invention, I contemplate providing means for removing the roof and charging the furnace through the opening thus provided. The charge can be deposited in several comparatively large quantities or even dumped into the furnace in one operation.

During this operation, there will be a high rate of heat dissipation from the furnace, but as the operation is accomplished in such a. short time, the total amount of heat lost will not be greater than in the conventional furnace in which a door is open for the long period required for charging.

In charging the multiple burner furnace,- I contemplate arranging the material in piles rather than distributing it evenly over the hearth. By piling the charge high between burners, cross channels are thereby provided in. front .of the burners to allow passage of the flames. This is desirable for example in an open hearth furnace when the charge consists mainly of small pieces .of scrap which pack closely together and prevent flames from penetrating readily into the pile. In this case, with the scrap piled in front of a burner, the flames would be deflected up into the roof and would thereby cause rapid deterioration of the roof refractories. By providing cross channels for the flames, the deflection into the roof is avoidframework 24.

ed and at the same time a greater surface is exposed for the flames to impinge upon, while the advantage of melting the scrap from the bottoms of the piles is retained.

I will now describe the construction and methods of operation of a furnace embodying the principles of my invention in connection with the following drawings. The embodiment shown and described is that of an open hearth furnace for the manufacture of steel, but it is to be understood that the principles will apply to other types of high temperature furnaces.

Figure 1 is a sectional elevation of an open hearth furnace, taken along line in Figure 2, showing the method of charging with the roof removed.

Figure 2 is a plan of the furnace showing the means for removing the roof. 1

Figure 3 is a longitudinal section along the line 3-3 in Figure 2, showing a method of charging the furnace in one operation.

Figure his a transverse section taken along the line 4-4 in Figure v3 showing the direction of the flames.

Figure 5 is a detail of the mechanism for elevating and moving the roof as viewed along line 55 of Fig. 2.

Figure 6 is a section of the mechanism taken along the line 6-6 in Figure 5.

Figure '7 is another method of elevating and moving the roof.

In Figure l the furnace I-having a hearth 2 is supported on steelwork 3 on a foundation 4. The furnace is provided with burners 5, 6 in the front wall 1 and in the back wall 8. The burners are supplied with fuel which is fed through a fuel pipe 9 which is shown as of the approximate proportions necessary for liquid fuel or gas of high fuel value.-

Air is supplied to the burners from a main air duct III which is located along the front of the furnace beneath the charging floor A branch |2 of the main duct extends around the end of the furnace behind the foundation pier 4 for supplying the burners in the backwall 8. This branch does not extend across the center of the furnace under the tap hole l3 but supplies only the rear burners on one-half of the furnace. The other half -of the rear burners are supplied by a separate branch duct (not shown). Individual ducts I4, l5 connect each burner with the supply duct.

Preheated air is conducted under a slight pressure from the air .preheater to the burner ducts. The air preheater (not shown) can be of any known type or it can embody one of the methods of preheating air shown in my copending application, Serial No. 672,545, filed May 24, 1933.

The roof [6 of the furnace is shown in the open position. It is of the flat suspended type, comprising a steel framework IT supporting a number of channel shaped cross members IB which carry the refractory pieces If) in suspension. The framework I! is carried on trucks 20, 2|, one truck supporting each corner of the framework. The trucks have wheels 22 which roll on a track 23 which is supported on a steel The framework 24 is elevated on upright members 25. There are two of such elevated rails, one under each end of the roof extending along the ends of the furnace and out over the tapping floor 26. By means of mechanism which will be described later, the roof can be first raised a few inches away from the opening.

furnace walls and then rolled away from'above the furnace.

Material for charging the furnace is brought in large drop bottom buckets 21, 28 carried on -flat cars 29. The buckets are filled in the yard with the materials for charging, such as, limestone, steel scrap, pig iron, etc. and transported on the fiat cars into the plant over the charging car track 30 to a position in front of the furnace The buckets are then lifted, one at a time, by means of a crane 3|, and after the roof has been rolled away, they are lowered into the furnace in the position shown. The'bottom 32 of the bucket 28 is then dropped by releasing the latch 33, allowing the scrap to drop down on the hearth 2, after which the bucket is 'raised out of the furnace and the roof replaced.

One method of .tripping the latch 33 is shown in Figure 1 and comprises a chain or cable 34 attached to the latch and extending up to the crane carriage, where it can be pulled by means of a motor driven winch (not shown). There are other methods which can be used in dropping the bot oms, another of which will be described later. The latch 33 could also be tripped by hand from the charging. floor by running the tripping cable 34 over a pulley on the crane.

The crane 3| can be of the two-hook type used in carrying hot metal ladies in present steel plants, one hook 35 engaging 2, lug 36 on each side of the bucket.

It is desirable to interrupt firing during the time that the roof is off.

After each bucket has been emptied, it is replaced on the fiat car 29 for refilling.

The charge in the buckets can be graded when the buckets are filled, so that the several materials will drop on the hearth in the desired arrangement. For example, the limestone can beplaced in the bottom of the buckets with the heavy scrap above the limestone and light scrap on top or in any other desired 'order.

Referring now to Figure 2, which is a plan of the furnace with the roof removed, the furnace is shown having four rear burners 6 and four front burners 5. The front burners are located between the doors 40, which can be placed farther apart than in the conventional furnace. The doors are placed farther apart -not only to allow room for the front burners,

but also to allow more space for the cross channels in the charge.

The furnace is shown asa one-way or unidirectionally firedfurnace having an exit port 4| at but one end of the furnace. A waste gas duct 42 leads downward fromthe exit port.

The construction of the roof is shown in this drawing. The frameworkv l1 comprises two longstructural members 43, 44 spanning the length of the furnace, tied together by cross members 45, 48. The roof refractories l9 are suspended from the cross channels l8, which extend be- The four trucks, 20, 20, 2|, 2|, one under each end of each main member, carry the weight of .the roof on two wheels each. The wheels 22 roll on the two rails 23, 23', which extend along each side of the furnace.

In order that the atmospheric leakage under the edge of the roof be minimized, during operation, an elevating mechanism is provided in reach of the trucks by means of which the roof can be elevated slightly above the walls of the furnace while moving but can be lowered into contact with the furnace walls during furnace operation.. This elevating mechanism, which will be described in detail later, is driven by motors 41, 48, one ateach end of the furnace. Each motor drives a cross shaft 49 through a reduction gear 50, the cross shaft in turn driving the mechanism 5! in both trucks at one end of the furnace.

The roof is moved by a third motor 52, which drives a longitudinal shaft 53 extending to one truck at each end of the furnace. The motor is connected to the shaft through a gear reduction 5 1. The shaft is geared at each end to one wheel of the truck through a gear reduction 55- in a manner similar to a traveling crane.

Power can be supplied to the driving mechanism through a number of trolley wires as also in the case of a crane 'or. by a flexible cable. Control of the roof movements is preferably accomplished from a position on the charging floor.

In Figure 3 is shown a method of charging the furnace in but one operation. In this case a number of charging buckets to 64 inclusive are supported in one framework 65, which in turn is lifted by a traveling crane 3i having two hooks 35, 35 which engage lugs 36 in the framework.

The bucket assembly is filled with charging materials in the yard and transported into the furnace on a large flat car, as described in connection with the individual buckets 2%.

Each bucket has two drop bottom doors 66, 6? to which are attached a pair of rods or chains at, 69. These rods or chains are joined together at their upper end and connected to a common chain 10 which passes over a pulley ii in the framework 65 and extends to a winch 12 at the end of the framework. The winch I2 is driven by a motor 13 through a self-locking worm gear, so that when the winch has wound up the chains, thereby raising the drop gates, the gates will remain closed until the motor is operated in the reverse direction to lower the gates. The winch and driving motor are. carried on an extension M of the frame 65 which extends out over the furnace end wall 15 when the buckets are lowered into the furnace, thereby protecting the motor and mechanism from the intense heat of the furnace. This motor ,can be controlled in any suitable manner such as, through a flexible cable from the charging floor.

The size and spacing of the buckets in the frame are governed by the desired arrangement of the charge in the furnace. Figure 3 indicates an arrangement of the charge lt with respect to the burners 6 and the approximate comparative size and spacing of the buckets to accomplish this result. For example, the three center buckets (ii, 62, 63 each must supply nearly twice as much scrap for piles which are heated by burners on both sides as the end buckets 66, 6t, each of which supplies a pile which is heated on'but one side and must, therefore, be correspondingly smaller. The spacing between the buckets is a factor in'determining the depth of channel between piles.

In Figures 2, 3, and (l, the straight arrows extending from the burners 5, 6 indicate the direction of flames. As the burners are slanted downwards, the flames impinge on the bottoms and sides of the channels in the charge. The burners can be one of the types of turbulent burners which are now in use in boiler furnaces for burning oil or gas. This type of burner has been found to provide substantially com plete combustion in about eight feet of flame travel; therefore, in an open hearth furnace,

combustion from each row of burners will take place in close contact with the charge and will be practically completed by the time the flames meet in the center of the furnace.

The. gases of combustion at this point will consequently. be inert and their energy spent, and will be forced upward by the force of the firing, as shown by the wavy arrows, where their damage to the roof refractories will be much lesssevere than in conventional type furnaces in which some combustion usually takes place in proximity to the roof and the impingement of the flames on the refractories causes rapid deterioration. The inert gases are then drawn out of the top of the furnace through the exit port 4i and the waste gas duct 32.

' It is understood, however, that although Figure 3 has been found convenient in which to illustrate the travel of the flames and gases, the firing would notgenerally be resumed in practice until the charging buckets had been removed and the roof replaced, as shown 'in Figure 4.

Although the piles of scrap are higher than in conventional type furnaces, the depth of scrap in front of the burners is less with the result that after it has been melted down, the depth of the bath needi'be no more than in present furnaces. The additional height of this furnace, however, permits a considerable leeway in the amount of scrap that can be charged. In present. furnaces this amount is limited by the height of the roof, under which combustion space must be provided, and by the mechanical limitations of the charging machine.

Whilev the roof is off the furnace, the heat stored in its refractories tends to dissipate and their temperatures tend to decrease. In the open hearth furnaces of the past design, wherein the roof is relied upon to confine the flames close to the charge, the roof temperature would have to be raised to normal before the full effect of the flame could be realized. By the present invention the flames act in'the manner of blow torches and their temperatures are much less affected by the temperature of the furnace roof, or walls. The present firing arrangement is therefore particularly advantageous in a furnace having a removable roof since, with this firing arrangement, the full effect of the flame may be had immediately after replacement of the roof following a removal for charging purposes, without delay due to cooling of the roof during the time that the roof was removed.

Figure 5 is a detail of the elevating and rolling mechanism at one corner of the roof asviewed on a line 5--'5 in Figure 2. Figure 6 is a section taken along line 6-6 in Figure 5.

threaded nut member 82 is supported by a pair of trunnions 83, 8% carried in bearings 85, 86 in the truck framework.

A vertical shaft 81, having a threaded end 88, is supported by the trunnioned member. 82 into which it is screwed. A disc 89, rigidly mounted on the shaft 81, forms the lower race of a ball bearing 90, the upper race 91 of which is fastened to the roof girder 44. The shaft extends up through the girder to a journal bearing 92 on top of the girder which acts to steady the shaft 81.

Hence, the roof frame rests on the screw shaft 81, which is rotatable in bearings 90, 92. By rotating the shaft, it is screwed upwards or downwards in the nut 92, which is supported on the truck 2|.

The shaft is rotated by means of a worm gear 93 mounted on the lower ball bearing race 39. A worm 94 meshes with the worm gear and is connected to the shaft 49, which was shown in Figure 2 to be connected to a motor 48 through a gear 50.

Hence, by rotating the motor, the two elevating mechanisms at one end of the roof can be simultaneously operated to raise or lower the roof and thus clear the wall refractories before the roof is rolled away. The motor atthe other end of the roof would be operated at the same time but not necessarily in synchronism.

Several inches clearance space 95 are provided between the nut 82 and the frame 80, so that longitudinal expansion and contraction of the roof is taken care of by the stub shafts 83, 84 sliding in their journals 85, 86. Lateral expansion and contraction of the roof merely causes a slight movement of the trucks along the track. Any strains which might be set up in the mechanism by one screw becoming slightly higher than the other are avoided by trunnioning the threaded nut in the truck frame.

Figure 6 also illustrates one of the methods of supporting the roof refractories I9 from the framework by means of cross-channel members I8. This type of suspension is known in the art and consists of rows of refractories 96 having projections which slip in between the channels, and alternate rows of filler pieces 91 which have provision for suspending them from the adjacent rows of suspension pieces 96.

In Figure '7 is shown one other method of raising the roof to clear the wall refractories before it is rolled away. In this drawing, which is an end elevation, the roof framework I1 is mounted on trucks 98, 99, but instead of elevating mechanisms in the trucks, the mechanism I is built into the track framework. The track is divided in two parts, one stationary portion ml, which is supported on a girder I02, which is in turn supported onupright members I03, I04. The other portion I of the track is carried on a girder I06 to which are fastened under each corner inclined plane members I01, I 08. These latter members rest on co-oper-ating movable inclined plane members I09, IIO, which rest on a stationary girder III supported on upright members H2, H3. The movable members I09, II 0 are adapted for horizontal movement along the girder III toward or away from each other and are moved by means of a cross shaft II 4, which is threaded on each end and screws into each of the movable members in such a manner that when it is rotated in one direction the movable members I09, IIO are drawn together, and in the other direction of rotation they are forced apart. When they are drawn toward each other, they slide on the cooperating inclined members I0'I, I08 and cause the girder I06 and, therefore, the entire roof to rise until the section of track I05 is brought to a level with the stationary track IN and at the same time the roof refractories are separated from the walls. The roof may then be rolled off the furnace on the stationary track.

In replacing the roof, it is rolled back and the movable wedges I09, IIO are forced apart, allowing the roof to lower to the walls of the furnace. Power for efiecting the elevation is supplied by a motor H5, which drives the shaft II4 through a gear reduction II6. Instead of the wedges shown, it is obvious that ordinary jack screws or hydraulic jacks could be used.

I do not intend to limit the use of this method of'charging to the novel type of furnace shown and described herein, as it can be adapted to other types as well. Furthermore, I do not wish to limit the method of arranging the scrap in the type of furnace shown and described herein to this method of charging, as the charge could be arranged in the described manner by means of a conventional or other types of charging machine.

What I claim, therefore, and wish to secure by Letters Patent is:

1. In combination with an open hearth furnace or the like having a row of spaced apart burners along each of two opposite sides of said furnace, means for arranging a charge to be melted in said furnace in piles between said burners with a channel in the charge in front of each burner.

2. In combination, a melting furnace having a hearth, means for arranging a charge on said hearth in a series of piles with channels in the charge betweensaid piles, and a row of burners disposed along each of two opposite sides respectively, each of said rows being spaced so that a pair of opposing burners is positioned in alignment with and directed to fire into each of said channels.

- 3. In combination with a melting furnace having a hearth, a removable roof, and a row of spaced apart burners along a. side of said furnace, means for arranging a charge in said furnace in piles between said burners, said means comprising a structuraLiramework, a plurality of buckets supported on said framework, said buckets being spaced to correspond to the spaces between said burners, and means for lifting said framework and buckets to a position over said hearth.

4. The method of charging a melting furnace having a row of spaced apart burners along each of two opposite sides of said furnace, comprising placing a charge in the furnace piled high between saidburners with a cross channel in the charge in front of each of said burners.

5. The method of charging a melting furnace having at least one pair of oppositely disposed burners, comprising placing a charge in the furnace piled high at each side of said burners with a channel in the charge extending between said burners.

6. The method of charging a melting furnace having a row of spaced-apart burners along one side thereof, and a second row of burners aligned in opposition to the first said row, on the opposite side of the furnace, comprising placing a charge in the furnace, piled high between adjacent pairs of opposing burners, with a cross ha'nnel in the charge extending between each pair of opposing burners.

7. The method of operating a melting furnace having a row of spaced 2,132.70 burners comprising placing a charge in the furnace piledhigh between said burners with a cross channel in the charge in front of each of said burners, and directing the firing at an angle downwardlyinto said channels.

8. The method of melting a charge on a furnace hearth, comprising, arranging said material in piles on said hearthwith cross channels between said piles and directing opposing streams of flames into each of said channels from opposite ends thereof.

,9. The method of melting a charge on a furnace hearth, comprising arranging said material in piles on said hearth with cross channels between said piles, directing opposing streams of flames into each of said channels from opposite ends thereof, the impingement of said flames being concentrated at the bottoms of said channels and at the bases of the adjacent piles.

10. In combination with a furnace having a hearth adapted for melting a charge of solid material, a row of spaced apart burners along a side of said furnace, and means for arranging a charge in said furnace in piles between said burners, each of said burners being directed to fire obliquely downward between two piles of said material.

11. In combination with a furnace having a hearth adapted for melting a charge of solid materials, a burner disposed in a wall of said furnace, a roof on said furnace, means for lifting and removing said roof, and means for depositing a charge on said hearth in an arrangement whereby the charge is piled high on each side of said burner with a channel in said charge in front of said burner, said burner being directed to fire toward the bottom of said channel.

12 In combination with a'furnace having a hearth for melting a charge of solid materials, a plurality of burners disposed in a wall of said furnace, a roof on said furnace, means for lifting and removing said roof, charging means for depositing a charge on said hearth through the top of said furnace with said roof removed, said charging means including means for arranging said charge in piles between said burners, forming a channel in front of each of said burners, said burners being adapted to direct flames toward the bottoms of said channels.

13. In combination with a furnace having a hearth for melting a'charge of solid materials, a row of burners in one wall of said furnace,'a row of opposing burners in the opposite wall of said furnace, a roof having elevating and propulsion means for uncovering said furnace, and charging means for dropping a charge on said hearth through the top of said furnacewhen said roof is removed, said charging means in cluding means for dropping said charge in theform'of alternate hills and valleys, a valley being located in alignment with each pair of opposed burners, said burners being adapted to fire obliquely downward toward the bottoms of said valleys.

14. A fuel fired open hearth furnace wherein flames are directed into the furnace to melt a charge and to maintain the temperature of the melt above the melting point of steel, and wherein additional material to be melted may be introduced even while the furnace contains a molten charge, said furnace having a roof removable for introducing a charge and replaceable, said roof comprising ,a framework and a refractory lining on the under side of the same, means for directing flames into the furnace in directing means longitudinally of the furnace whereby the products of combustion travel through the furnace in a longitudinal direction, the flame being directed obliquely downward into the furnace from a level substantially below that of the top of an unmelted charge, and a roof for confining the products of combustion in their longitudinal travel, the flame being of amagnitude and intensity sufficient to raise the charge to a temperature required to melt steel, characterized by the fact that the roof is removable and is located appreciably above the level reached by any substantial part of the flames, to preclude impingement of intensely hot burning gases upon the roof of the furnace, and there is provided means for removing the roof from the furnace for permitting the introduction of a charge into, the furnace.

16. A furnace including a row of burners for directing flames into the furnace and having a removable roof, means for removing the roof, and means for placing a charge of raw material into the furnace comprising a movable bucket assembly movable into a position extending substantially the full length of the furnace and having controllable discharge members over the spaces betweenconsecutive burners for placing maximum charges between consecutive burners and minimum charges in front'of the respective burners.

17. The method of charging raw material into an open hearth furnace of the type having a row .of burners for directing flames into the furnace, which comprises, removing the roof of the furnace, moving a charge of raw material into the space vertically above the shell of the furnace, dropping the material to form ridges extending across the furnace between adjacent burners and channels in front ofv the respective burners, and replacing the roof.

18. The method ,of melting a charge in an open hearth furnace which comprises arranging the material in piles extending across the furnace with channels between adjacent piles, di-

recting opposing streams of flames into each of said channels from opposite ends thereof,

' substantially completing the chemical reaction of combustion of the flames by the time the ggases reach the upper level of the piles, and

points along one side of said furnace and from a second row of firing points located in the opposite side of said furnace, the points'in said second row being staggered in relation to the points in said first row, whereby the impact of said gases of combustion against the surface of the bath sets up local paths of circulation in the bath and thereby provides a stirring action.

20. In combination with a furnace having a hearth for refining a bath of molten metal, means for directing streams of flames and gases of combustion obliquely downward to the surface of the bath, said means comprising a plurality of burners arranged along one side of the furnace, and other burners firing similarly from the opposite side of the furnace but staggered in relation to the first mentioned burners, whereby the impact of said gases of combustion against the surface of the bath sets up a circulation in the bath and thereby provides a stirring action.

21. The method of refining a bath of molten metal in an open hearth furnace which includes directing streams of flames and gases of combustion obliquely downward to the surface of the bath from a first row of firing points along one side of said furnace and from a second row of firing points along the opposite side of said furnace, the firing points of said second row being staggered in relation to the firing pointsof the first said row, whereby the impact of said gases of combustion against the surface of the bath sets up local paths of circulation in the bath and thereby provides a stirring action which tends to accelerate the contacting action of the various ingredients of the bath and thereby to accelerate the rate of chemical reaction between them.

ALLEN M. ROSSMAN. 

